Since IEEE 802.11n is still in draft, and the vendors have a nasty habit of ignoring the specification (e.g., 802.11g is actually 22Mbps, not 54Mbps -- that's "Wireless-G"), you're going to run into issues.
Furthermore, check your "Wireless-N" access point (or low-end router) is actually supporting 802.11b/g, some have options to actually turn it of (and may for maximum performance reasons).